Diabetes is a disease where the body either does not produce or does not use insulin properly. Insulin is made in the pancreas and is used to convert sugars into energy. There are two types of diabetes. Type I is a condition with which people are born. Their bodies do not produce insulin and, therefore, they must have daily insulin injections. Type II develops as a person ages and his or her body no longer uses the insulin effectvely.
Sources:
http://www.diabetes.org/about-diabetes.jsp
http://diabetes.webmd.com/tc/type-2-diabetes-living-with-the-disease-frequently-asked-questions